Democratic gubernatorial candidate Joe Avellone is protesting the party’s nomination threshold, saying it plays into the hands of political insiders and better-known candidates.

Avellone, a biopharmaceutical executive waging a long-shot bid for the nomination, said that party rules setting prohibitions for candidates to reach the ballot had altered his campaign strategy, prompting him to campaign among Democratic activists instead of “voters all across the Commonwealth.”

Party rules require candidates to obtain 15 percent of the delegate vote on the first ballot at the state Democratic convention, held this year on June 14. That benchmark could sharply limit the Democratic primary field.

In a post on the liberal Blue Mass Group blog, Avellone said the new threshold “would limit participation in our democratic process and it would go against our ideals of fairness and equality.”

“I’m not looking for pity,” Avellone wrote. “I’m looking for a fair shot. When I entered this race I knew that I faced an uphill battle, but the rules changed midway through the game, and the hill only got bigger.”

In an interview Friday, Avellone said the threshold “stacks the deck against new faces or new ideas.”

Avellone said he had sent a letter to party delegates urging them to reconsider the rule, which had come before the party committee for reconsideration last year but been rejected.

Avellone, along with former federal health care administrator Don Berwick and former homeland security official and Globe columnist Juliette Kayyem, have struggled to gain the name recognition enjoyed by two other Democratic hopefuls, Attorney General Martha Coakley and Treasurer Steve Grossman.